In one narration the words are: The Prophet (peace and blessings be upon him) offered prayers together during a journey. Imam Ahmad recorded both narrations, and the chain of both contains a narrator, al-Hajjaj bin Artah, about whom there has been criticism.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2962